I'm standing in what used to be a banking hall. But today, it's more like a basilica – a cavernous, vaulted space dripping with classical detailing, from its giant arches to its marble panelling to its gilded capitals. Except that there are some decidedly 21st-century additions. Strange, angular forms like giant Toblerones snake through the air, while a mezzanine platform echoes their trapezoidal shapes in black wood and golden grilles.

This could be a chic cocktail bar in the trendiest part of Paris – but it's actually a youth centre in downtown Norwich. In the building's heyday, bank managers would look on as Norfolk farmers deposited their hard-earned cash. Now it's more likely to be hosting 1,500 teenagers bouncing around to Basshunter. Youth centres, it seems, are changing.

Apart from the school and the home, most of our built environment ignores young people unless they have money to spend, which they usually haven't. We always seem to look for ways to "keep them off the streets", but where else can they go? This is especially true in Norwich, where the town centre can get pretty rowdy at the weekend; binge-drinking and teenage pregnancy rates are higher than average, not to mention the usual teen pitfalls of drugs, crime and antisocial behaviour. Boredom is part of the problem, the common complaint being: "We had nothing else to do."

The Open youth centre in Norwich is the first of what is hoped will be a new generation of 21st-century youth venues. Since it opened late last year, it's been attracting growing numbers of 12- to 25-year-olds, and hosting sell-out events – not just gigs like Basshunter's, but regular under-18s club nights and events with local bands. And it's not just the young who are flocking there: architects, politicians and community groups from across the country have been descending on the centre to see if what's been done here can work elsewhere.

Open was part-financed by the government's "myplace" initiative (small letters and joined up, for extra youth-friendliness), which is being billed as the largest ever government investment in youth facilities. Myplace is putting £270m into creating (or improving) youth venues around Britain, with some 60 projects under way. Another opened recently, in King's Cross, London: the refurbishment and extension of the New Horizon youth centre, by Adam Khan Architects. It's a friendly, almost quaint-looking, barn-like building, its steeply rising copper roof concealing a tall, angular, wood-lined venue space.

Judging by these and other designs made public so far, this initiative could put paid to the abiding image of the youth centre as a cold prefab with leaky toilets and a threadbare pool table. Largely the work of young, up-and-coming architectural firms in partnership with graphic designers, the new youth centres are vibrant, colourful and bold – youthful, you could say.

One of the main reasons for this is that most of the myplace schemes are being designed with a high degree of input from young people themselves. In many instances, following a precedent established by Open, local youth forums have been established to work with the architects. And these "client groups" have been pushing their designers to go further.

In Torbay, for example, the youth team rejected architects Feilden Clegg Bradley's original proposal for a flat roof in favour of an irregular jagged profile. In Trafford, they approved of a scheme by Ellis Williams that resembles a cluster of children's building blocks. In Brent, they plan to use the rubble from the old youth centre to make a hill outside the new one, where people can watch outdoor performances. Slightly more outlandish is the Sutton Life Centre, an ambitious project planning to incorporate an "experiential citizen zone" – a mocked-up indoor street, like a movie set, where children will be able to rehearse "life skills", through simulated encounters with virtual drug dealers and gang members.

Open's youth forum, consisting of about 40 people between the ages of 12 and 18, had a say in everything from what activities should go on inside to the graphics, signage and furniture. They even selected the designers: Hudson Architects. Their key demands, says architect Anthony Hudson, were bright colours, decor that spoke to their demographic, plus music and media facilities, a climbing wall, and (high up the list) good toilets.

These demands have been met, without going overboard. Outside, Open is a stern, Edwardian-looking building; inside it's bursting with playfulness. Funky furniture abounds; on the walls there is bespoke graffiti and Shepard Fairey's Obey artwork. The signage is big and bright. It's not a circus – it feels quite calm – but neither does it conform to sober, grown-up expectations.

The main banking hall is a prime example. It is not so crazy that an adult wouldn't dream of setting foot in there (in fact, conferences have been hosted here). But the architects were told: be bold. When their young clients saw the hall in its original state, Hudson says, the only aspect of the antiquated, Grade II-listed interior they really liked was the gold leaf. So it lives on in the gold-plated Toblerone bars (actually acoustic baffles), a 21st-century echo of 20th-century bling.

"The kids wanted more radical ideas than the trustees," says Hudson. "A lot of the time you're thinking, 'Is this exciting enough for them?' We've got quite a young team but we all did things like going nightclubbing for research, just to make sure of the levels we needed to hit."

Other areas are similarly refreshing. The social hub is a cafe adjacent to the banking hall, in what used to be the backyard. This skylit space has a deliberate outdoor feel: white wall tiles, grass-like green carpeting, lamp-posts. But rising through it, rather surreally, is a climbing wall. It's a delightful touch – in a regular building, you'd probably just stick in an atrium. On the mezzanine there's a media lab, where schoolkids are playing a shoot-'em-up computer game.

In the basement there's even a fully kitted-out nightclub with an industrial aesthetic, all dark wood and galvanised metal. But doesn't this make Open a binge-drinker's paradise? Not really – the bar only serves juice.